Being in a tuning environment all day everyday I get asked alot for information on knock frequency, intensity and how to set up monitoring devices properly.
When using Knock monitoring systems you need to input a frequency to monitor use this guide as a starting point. I often get called and asked what starting point to use as it is not something that is easy to find in any literature, i have put together a list of my starting points for a few different engines.
If the engine is not listed just ask and i will add it to the list (only takes a few minutes to work it out).
RB20 7.3khz
RB25 6.7khz
RB26 6.7khz
RB26 (forged) 6.6khz
RB28 6.6khz
RB30 6.7khz
RB30 (forged) 6.6khz
VG30 6.6khz
VR38 6.0khz
VR38 (4l) 6.0khz
VQ20 7.5khz
VQ30 6.2khz
VQ35 6.0khz
SR20 6.7khz
SR20 (2.2l) 6.6khz
SR20 (2.35l) 6.3khz
CA18 6.9khz
2JZ 6.7khz
2JZ (forged) 6.6khz
2JZ (3.4l) 6.6khz
1JZ 6.7khz
B16A 7.1khz
LS1 5.8khz
LS2 5.7khz
XR6T 6.2khz
XR8 (modular) 6.4khz
The first post above is made to centre the frequency @ an approximate target. The bandwidth control is then used to determines how far above and below the centre frequency the device will detect, i.e. the width or spread of frequencies.
A narrow bandwidth adjustment is very specific, useful for accurately accentuating a specific knock frequency (if you know it). Narrow bandwidth adjustments tend to have less noise.
A broader bandwidth allows more frequencies to be heard, useful for a new set-up where the actual frequency is not known or for initial testing and finding the correct centre frequency. Broader adjustments tend to have more "noise".
There is no correct Bandwidth per see but the narrower the bandwidth the less feedback or noise will be recorded or heard. Nice for loose or noisy solid cammed type engines that naturally emit lots of mechanical noise.
Below is a diagram:
Yellow vertical line is the centre frequency (in this case 6khz)
Red horizontal line is narrow bandwidth
Green horizontal line is broad bandwidth
Here are two sound files
click here for sound file 5000rpm heavy constant knock
click here for sound file 2500rpm knock induced mid way through sound file then timing backed out to stop it
Tools for listening to KNOCK
GIZZMO K-MON
THE KNOCK BOX
i have both of these now for listening to Knock, cant be too safe